Electromagnetic device



Dec. 13, 1938. E. J. PRATT ELECTROMAGNETIC DEVICE Filed Sept. 11, 1936 ZSheets-Sheet l @QQQF INVENTOI? By E. J. PRA 7'7: 6?.M

? ATTORNEY D .13,-193s. E1 PRATT f 2,140,139

ELECTROMAGNET I C DEVI G E Filed Sept. 11, 1956 2 Sheets-Sheet 2 /Nl EN7'OR .E. J. PRA 77' y aam A TTORNE V Patented Dec. 13, 1938 UNITED STATES PATENT OFFIQE ELECTROMAGNETIC DEVICE Edward J. Pratt, New

Bell

York, N. Y., assignor to Telephone Laboratories, Incorporated,

6 Claims.

This invention relates to switch telegraph apparatus and, particularly, to electromagnetic selective devices especially adapted therefor.

The present invention has for its salient object the provision of a materially simplified electroresponsive selecting device which is highly sensitive, is rugged in construction, and is capable of operating efficiently at high speeds.

One of the features of my invention is the use of a permanent magnet and associated polepieces which can be removed as a unit from the rest of the relay structure, thus facilitating the manufacture and assembly of the separate parts, reducing its cost of production and making it easier to maintain in service.

Another feature of my invention is a novel construction of the pole-pieces which are so formed as to include a spring pressing upon a locking nut that idles upon the pole screw so as to prevent said pole screw from losing its adjustment.

The above and other objects of the invention are attained in an electromagnetic device provided with a unitary magnet and pole-piece structure which is held to and can be removed from the remainder of the relay assembly by the manipulation of four screws located at the base of the relay frame. The permanent magnet is made of thin sheet stock to which are secured L-shaped pole-pieces. Within the space bound by the inner surface of the magnet is an energizing coil which encircles an armature of relatively small cross-section secured beyond the coil to a magnetic iron block supported on the rear of the magnet. The free end of the armature cooperates with the face of either leg of the polepieces to form a path for the magnetic flux between the'armature and the pole-pieces when the armature is moved in response to the current flowing in the energizing coil. The return polepieces are formed with a U-bend through which a hole is tapped for the pole screw. The width of the U-bend is sufficient to permit a nut to be assembled on the pole screw without binding on the pole-piece. That is, the nut thus assembled does not interfere with the free turning of the pole screw. This nut projects beyond the edge of the pole-piece so that a steel spring which presses against the nut with considerable force will hold the nut in position, and the steel springs are made sufficiently strong to provide the pressure required for the necessary friction to hold the pole screw in adjustment.

A more thorough understanding of the invention will be had from the following description,

taken in conjunction with the accompanying drawings wherein,

Fig. 1 is a perspective view of a preferred form of construction embodying the invention;

Fig. 2 is an exploded view of Fig. 1 particularly showing the movable magnet assembly;

Fig. 3 is an exploded perspective view of the parts comprising the magnetic unit;

Fig. 4 is a partially sectional side elevation of the relay structure showing the cover in place; while Fig. 5 is a detailed front view of one of the polepieces, showing its mode of construction and the means used to maintain the pole screw of the relay in a given adjustment.

Referring now to the drawings in which the numeral designations refer to the identical elements shown in each of the figures, there is shown a relay frame having a base 5 of brass or other non-magnetic material to the front end of which are secured the bracket members 21 by screws 36. The bracket members are insulated from the base 5 by insulating plates 31. Each bracket member carries in its upper end a terminal screw 25 provided on its inner end with a contact point and on its outer end with a finger wheel 3| of insulating material. By means of the finger wheels the terminal screws may be adjusted to regulate the separation between the contact points and the contact springs carried by the free end of the armature 18.

The rear end of the base 5 is bent upwardly at right angles to form a back plate 33 which is provided with threaded holes 1 by means of which the relay may be attached to any suitable support such as the support I. The support I is of insulating material and is provided with terminal plugs 34 by which electrical connections may be made to the coil terminals and contacts of the relay and also with holes registering with holes 5' of back plate 33. Interposed between the back plate 33 and support I is the end plate 2 of a cover 32 also provided with holes which register with the holes I in the back plate 33. The back plate 33, cover plate 2 and support I are secured together by screws which pass through the alined holes therein and through spacing washers 3 and 4. The washers 4 are of insulating material whereby the cover plate 2 is effectively insulated from the relay.

The magnet structure, as disclosed assembled in the upper portion of Fig. 2 and disassembled in Fig. 3, comprises a front base block 20 of brass and a rear base block l3 of magnetic material joined by two L-shaped return pole-pieces I2. 55

The pole-pieces are secured to the front base block by screws 2i and to the rear base block l3 by brass screws 39. The pole-pieces are separated from the rear base block l3 by interposed brass shims is which constitute magnetic air gaps. Secured to the outer faces of the poleces 52 by screws II is a U-shaped permanent nagnet i 9 made of sheet magnet steel. The rear block 13 is provided with an ear l between which and the clamping plate IS the end of armature is secured by screws 29.

The forward upwardly extending arm of each of the pole-pieces I2 is turned inwardly and downwardl to form a U-bend ll of sufficient width to embrace a locking nut 25. Threaded through the two portions of the U-bend and through the embraced nut 25 is a pole screw l6. For engagement with each of the locking nuts 25 a stiff as. r,

s-eel spring 24 is provided, each spring 24 being ,ired at one end to the front face of base a screw 35. When either of the pole i8 is turned to provide the required airbetween the face of the armature l8 and the face of the pole screw, the spring 24 presses with a predetermined pressure against locking nut 25 mounted on the pole screw which is in turn pressed against the threaded surface of the screw. This prevents the pole screw from turning one way or the other under the influence of vibration or other field conditions impracticable to control and thereby tends to cause the pole screw to be retained in its original adjustment.

The magnet coil 23 is mounted on a holder CO1 prising two end supports 38 each provided with threaded apertures 28 and joined by a tubular sleeve 22 through which the armature l8 may freely pass.

The entire magnet structure comprising the various parts as above described and as shown in d tail in Fig. 3 is assembled into a unit structure as shown in the upper portion of Fig. 2 by the sets of screws 21, II, and 39 passing through tl e apertures of each pole-piece 12, but the armature i8 is not attached. The magnet structure is then lowered into place to surround the coil the four tapped holes (not shown) in the lower surfaces of the front and rear base blocks 3 and i3 registering respectively with the four ."cures 28 of the coil supports 38 and cooper- .nd the magnet unit are then secured to the base by the screws 9. The armature I8 is then inserted through the sleeve 22 and is secured to the ear 55 b the screws 29. The pole screws l6 are then turned against the pressure of the springs 24 communicated to the lock nuts 25 to provide pole face separation between the armature and the pole screws and contact adjustment is then made between the armature contacts 39 and the terminal screws 26 by turning the finger wheels 3|. A cylindrical cover 32 may be provided with projections that fit into the notchings of cover plate 2 to completely enclose the relay.

When for any reason it becomes necessary to inspect the relay or possibly to replace the magnet unit by another, it is only necessary to remove the armature from the coil sleeve 22 by loosening the screws 29 and remove the screws 9 which hold the magnet unit to the frame after which the unit may be lifted from the relay base and replaced in the manner already described.

What is claimed is:

1. In an electromagnetic device, the combination with an energizing coil having an armature extending therethrough, of a removable magnetic structure comprising two pole-pieces each formed with a U-bend having apertures therein, polescrews threaded through said apertures, a nut disposed within each of said bends and assembled on each of said pole-screws, and means for applying pressure to each of said nuts to hold each of said screws in an adjusted position.

2. In an electromagnetic device the combination with a supporting base, an energizing coil and an armature extending therethrough, of a unit magnetic structure comprising two L- shaped pole-pieces, a rear block, a front block, non-magnetic shims, means for securing said rear block to the rear end of said pole-pieces with one of said shims intermediate each two adjoining surfaces, means for securing said front block to said front end of said pole-pieces, a U-shaped member adapted to inclose said energizing coil secured to the outer surfaces of said pole-pieces, means for clamping said armature to said rear block, and means for removably securing said unit magnetic structure to said supporting base.

3. In an electroresponsive device, a pole-piece formed with a U-bend, aligned tapped apertures through said U-bend, an adjusting screw threaded through said apertures, a nut assembled on said screw and disposed within said U-bend, and means for applying pressure to said nut to hold said screw in any adjusted position.

4. In an electroresponsive device, a magnetic structure having pole-pieces formed with U- bends, aligned tapped apertures through each of said U-bends, an adjusting screw for each bend threaded through its respective apertures, a nut assembled on each of said screws and disposed within each of said U-bends, and a spring for each nut supported on said magnetic structure for applying pressure to said nut for holding its associated screw in any adjusted position.

5. A relay device comprising a non-magnetic chassis having a base portion and a back portion, an energizing coil mounted on said base portion, a magnetic structure including a U-shaped permanent magnet adapted for attachment to the upper surface of said base and removable as a unit therefrom, said magnetic structure in combination with the upper surface of the base of said chassis being adapted to surround the winding surface of said coil, and an armature connected to said magnetic structure and extending through said energizing coil to form with said magnetic structure the complete magnetic circuit of said relay device.

6. A relay device comprising a non-magnetic chassis having a flanged base and a rectangular back plate integral therewith for the support of said device, an energizing coil mounted on said base portion, a magnetic structure attachable to and removable from said base portion as a unit to inclose with said base the winding surface of said coil, said magnetic structure comprising a front block, a rear block, L-shaped pole-pieces attached to said blocks, and a U-shaped permanent magnet attached to said pole-pieces, and a reed armature extending through said energizing coil and secured to the rear block of said magnetic structure.

EDWARD J. PRATT. 

